Black immigrants are not struggling in America - it is only the native born blacks. Liberals have been mocking conservatives for decades about the conservative claim that welfare leads to dependency and broken families, but the relative success of black immigrants is a powerful testimonial otherwise.
Regardless of where they come from, the issue is one of how they 'arrive.' If someone, from anywhere, comes to the US thinking that once they cross the border (legally) all their problems will be solved and everything will fall into place, then they will fail. If they come with the thought that their success is dependent on them, then they will most likely find great success.
It's true. There is enormous resentment for Caribbean and African blacks who come to America and kick ass economically through--ta-da!-HARD WORK. What a concept.